This invention relates generally to improvements in irrigation sprinklers of the so-called micro-stream type having a rotatably driven vaned deflector for sweeping a plurality of relatively small water streams over a surrounding terrain area to irrigate adjacent vegetation. More specifically, this invention relates to an improved rotating stream sprinkler having a turbine driven gear drive arrangement for regulating the rotational speed of the vaned deflector to a controlled and relatively slow rate for sweeping and distributing the water streams relatively slowly over the adjacent landscape.
Rotating stream sprinklers, sometimes referred to as micro-stream sprinklers, are well known in the art of the type for producing a plurality of relatively small outwardly projected water streams swept over surrounding terrain for landscape irrigation. In one common form, one or more jets of water are directed upwardly against a rotatable vaned deflector which has a vaned lower surface defining an array of relatively small flow channels extending upwardly and turning radially outwardly with a spiral component of direction. The water jet or jets impinge upon this array of vanes to fill the curved flow channels and to impart a rotary drive torque for rotatably driving the deflector. At the same time, the water is guided by the curved flow channels for projection generally radially outwardly from the sprinkler in the form of a plurality of relatively small water streams to irrigate adjacent vegetation. As the deflector is rotatably driven, these small water streams are swept over the surrounding terrain area, with a range of throw depending in part on the channel configuration. Such rotating stream sprinklers have been designed for irrigating a surrounding terrain area of predetermined pattern, such as a full circle, half-circle, or quarter-circle pattern. For examples of such rotating stream sprinklers, see U.S. Pat. Nos. 4,660,766; 4,796,811; 4,815,662; 4,971,250; 4,986,474; Re. 33,823; U.S. Pat. Nos. 5,288,022; 5,058,806; 5,845,849; and 6,244,521.
In rotating stream sprinklers of this general type, it is desirable to control or regulate the rotational speed of the vaned deflector and thereby also regulate the speed at which the small water streams are swept over the surrounding terrain. In this regard, in the absence of speed control or brake means, the vaned deflector can be rotatably driven at an excessive speed up to and exceeding 1,000 rpm, resulting in rapid sprinkler wear and distorted water stream delivery patterns with reduced projected range. A relatively slow deflector rotational speed on the order of about 4-20 rpm is desired to achieve extended sprinkler service life while producing substantially uniform and consistent water stream delivery patterns. Toward this end, a variety of fluid brake devices have been developed wherein a rotor element carried by the vaned deflector is rotatably driven within a closed chamber containing a viscous fluid. In such designs, the viscous fluid applies a substantial drag to rotor element rotation which significantly reduces the rotational speed of the vaned deflector during sprinkler operation.
While such fluid brake devices are effective to prevent deflector rotation at excessive speeds, the actual rotational speed of the deflector inherently and significantly varies as a function of changes in water pressure and flow rate through the sprinkler. Since these parameters can vary during any given period or cycle of sprinkler operation, corresponding changes or fluctuations in the water stream delivery patterns can and do occur to result in inconsistent and sometimes inadequate irrigation of adjacent vegetation. In addition, such fluid brake concepts require the use and effective sealed containment of a viscous fluid such as a silicon-based oil or the like, which undesirably increases the overall complexity and cost of the irrigation sprinkler.
There exists, therefore, a need for further improvements in and to rotating stream sprinklers of the vaned deflector type for sweeping a plurality of relatively small water streams over a surrounding terrain area, particularly with respect to rotatably driving the vaned deflector at a controlled and relatively slow rotational speed to achieve improved and consistent water distribution with a substantially maximized the range of the outwardly projected water streams. The present invention fulfills these needs and provides further related advantages.